The invention relates to self cooling and self heating containers, and in particular to reusable self-heating and self heating sorption containers which operate without valves which perforate the surfaces of the device. Previous inventions relating to sorption self cooling and self heating containers have been described by the present author in U.S. Pat. Nos. 4,250,720, 4,736,599, 4,928,495, 5,079,932, and 5,168,708. Essentially, the self cooling and self heating containers consists of a chamber containing water, the boiling point of which has been lowered by an air vacuum in the chamber. The chamber communicates through a pipe with another chamber containing a desiccant. As the water boils it cools itself and absorbs heat from a food or a beverage which is preferred to be consumed at low temperatures. The vapor generated by the low boiling point water is removed by the desiccant. The vapor sorbed by the desiccant heats the desiccant. The desiccant then delivers heat to a food or a beverage which is preferred to be consumed at high temperatures. By closing the communication between the water and desiccant chambers the self cooling and self heating device can be stored indefinitely without losing its temperature changing potential. The cooling or heating action is initiated by opening of the communication between the water and the desiccant chambers. Thus, a reversible closing of the communication between the water and the desiccant chamber is essential for the storage and operation of the device. This has been previously achieved by valve means which open and close the pipe between the chambers.
The air vacuum which is required to lower the boiling point of the water, must often be maintained through out months or even years of the shelf life of the food or beverage. To prevent an air leak into the system through the valve an air tight and leak proof valve is essential. Standard valves which are manipulated through means which have perforated the wall of the temperature changer present a continuous leak hazard and are not suited for such strict and long term vacuum requirements. Commercially available vacuum valves are too expensive for use in or commonly used beverage containers. In the recent U.S. Pat. No. 5,168,708 the present inventor described a pliable outside surface, such as a bellows, as means to open and close the communication between the water and desiccant chambers without perforating the surfaces of the chambers. The air vacuum in chamber 11 causes a pressure differential between the inside and the outside of bellows surface 52. The pressure differential tends to keep the bellows in its folded position during storage of the device and a manual effort is required to pull the bellows outward to an extended position. The main objective of the present invention is to provide effortless magnetic means to open and close the communication between the chambers while maintaining the integrity of the chambers surfaces.